長期以來政府在從事運輸投資計畫之經濟效益評估時，往往僅考慮、興建與營運成本以及可衡量之效益－通常包括運輸時間節省及運輸成本節省，或者再加上肇事成本減少之效益而已，僅有少數計畫曾企圖將空氣污染及噪音改善方面的效益亦納入，其餘大部分之外部性皆視之為不可貨幣化的成本(效益)而予以忽略，極易造成資源使用之扭曲與錯誤的決策。事實上，未考慮的外部性中，運輸設施對都市空間之阻隔非常重要，因為空間阻隔的去除常為都市運輸投資計畫的原始動機，故如未將之納入評估中時，將導致。經濟效益評估與計畫內容脫節的現象。因此，本研究嘗試就運輸設施所造成空間阻隔之貨幣化成本的估計方法作－初探，並試以高雄臨港線鐵路發展成輕軌系統為例，進行－涵蓋較全面外部性之經濟效益之估計，其中包括肇事、空氣污染、噪音及運輸設施對空間之阻隔等外部性。空氣污染、噪音、空間阻隔等係以高雄市之實際資料透過Rosen(1974)的房屋特徵價格法 (hedonic price method) 來求得市民的願付價格，肇事成本則引用過去之相關研究。實證分析結果顯示：(1)運輸設施所造成空間阻隔對高雄房價的影響相當大，約在8%至24%之間；(2)高雄市民對空氣污染的評價以TSP、PMI0與CO為較重視，其房屋價格彈性分別為-0.455、-0.347與-0.132，皆對房價有相當程度的負面影響；(3)在噪音方面，發現高雄市居民以「靠近市區」與「交通便捷」為購屋首要要素，除非住宅噪音環境大於67分貝以上才會有較高的房價跌幅；(4)臨港環線輕軌之經濟效益評估結果顯示，空氣污染、噪音、肇事、空間阻隔方面獲致改善之效益占輕軌計畫總效益高達41.2%~ 42.6%，比重相當大，實不宜輕易忽視之。

For decades, when conducting cost-benefit analysis on transportation investment projects, the government tends to consider only the construction cost, operating cost and measurable benefits such as travel time, cost savings, and the reduction of traffic accidents. Only few projects try to include benefits on improvement of air and noise pollution control. Most of the other externalities are regarded as non-quantitative costs (benefits) and thus ignored. This would result in the distortion of resource allocation and biased policy decisions. In fact, among the ignored externalities spatial separation caused by transportation facilities is very important. The relief of spatial separation is often the motive for investing in an urban transportation project. Failure to consider the relief of spatial separation will result in the distortion of the cost-benefit analysis and project contents. Thus, this study aims to measure the monetary value of the improvement on spatial separation caused by transportation facilities. Using the light rail project in Kaohsiung as an example, we didαn economic benefit analysis which includes a more complete list of externalities. These externalities include traffic accidents, air pollution, noise pollution, and spatial separation caused by transportation facilities. The WTP price for air pollution, noise pollution and spatial separation are estimated using actual data of Kaohsiung through the hedonic price method. Traffic accident costs are estimated using outcomes of past studies. The conclusions of the present study are as follows:(l) Spatial separation caused by transportation facilities is about 8%~24%, having a great influence on housing prices.(2) The key factors that inhabitants of Kaohsiung consider in purchasing their houses are“near downtown” and “transportation convenience”. However, if the traffic noise exceeds 67dB, it would begin to have negative impact on housing prices.(3) The elasticity of housing price with respect to TSP, PMIO and CO are estimated as - 0.455, -0.345 and - 0.132, respectively, all have notable negative influences on housing prices(4) Results of cost-benefit analysis indicated that benefits estimated from the improvement of air pollution control, noise pollution control, traffic accident, and spatial separation constitute about 41.2 % ~ 42.6 % of the total benefit of the light rail project, which is a high percentage and should not be ignored.